Discrimination against pit bulls often has deadly consequences for the dogs.

Pit bulls can be affectionate, docile pets, but you wouldn’t know it from the public perception and media coverage of them.

You also might not know how these dogs are penalized—or how that penalty spreads to dogs who just happen to look like them. In a paper published in The Veterinary Journal, researchers say animal shelter staff frequently mislabel non-pit-bull dogs as pit bulls.

“Pit bull” is not a breed but a type that describes several breeds.

The American Staffordshire terrier, Staffordshire bull terrier, and American pit bull terrier are all pit bulls. These dogs have been maligned as violent and aggressive by nature—a reputation they have not earned. But news reports disproportionately report the culprits of dog attacks as pit bulls, even when, as scientists note, it’s unlikely that most of them are. As the researchers cite, about 46 percent of American dogs are mutts, but 90 percent of dogs named by the media in attack stories were labeled with a single breed or type (often pit bull). The numbers just don’t add up, they say.

Discrimination against pit bulls often has deadly consequences for the dogs.

There are outright bans on pit bulls in some parts of the country, which means that shelters won’t take them in, and they’re more likely to be put down. But many places rely not on evidence but on educated guesses and gut feelings to determine which dogs are pit bulls and which aren’t.

“Unlike many other things people can’t quite define but ‘know when they see it’

Identification of dogs as pit bulls can trigger an array of negative consequences, from the loss of housing, to being seized by animal control, to the taking of the dog’s life,” lead author Julie Levy said in a press statement. “In the high-stakes world of animal shelters, a dog’s life might depend on a potential adopter’s momentary glimpse and assumptions about its suitability as a pet. If the shelter staff has labeled the dog as a pit bull, its chances for adoption automatically go down in many shelters.”

Levy and her colleagues suspected that many shelter pit bulls were being mislabeled.

They wondered just how consistently and accurately veterinarians and shelter staff could identify pit bull breeds.

To find out, they went to four Florida animal shelters, which in the previous year had admitted from 2520 to 10,154 dogs. They recruited 16 workers at each, including four veterinarians, who were tasked with labeling newcomers to their shelters. Each participant completed a questionnaire about their shelter experience and any training they might have had in breed identification.

At each shelter, the researchers picked out 30 dogs of all different sizes, shapes, and colors, and noted how each dog had been identified.

They brought shelter workers from cage to cage and asked them to name each dog’s breed based on its appearance. If the assessor felt strongly that the dog had a secondary breed, they could note that. “Mixed breed” was also an option when they had no idea.

A vet on the research team examined all of the dogs, noting their height, weight, age, color, and other characteristics. The vet also drew a small amount of blood from the dogs and sent it to a lab that could test their DNA.

The researchers’ hypothesis was correct.

“We found that different shelter staffers who evaluated the same dogs at the same time had only a moderate level of agreement among themselves,” Levy said in the press release. And they fared even worse against the DNA analysis.

Shelter workers were able to spot real pit bulls and pit bull mixes 33 to 75 percent of the time, depending on the worker.

But they labeled non-pit-bull dogs as pit bulls up to 48 percent of the time. That’s almost a 1 in 2 chance that a dog with no pit bull DNA could be lumped in with the unfortunate pit bulls.

Pit bull DNA does not mean that a dog will be aggressive—and neither does simply looking like a pit bull. “A dog’s physical appearance cannot tell observers anything about its behavior,” Levy said in the press release. “Even dogs of similar appearance and the same breed often have diverse behavioral traits in the same way that human siblings often have very different personalities.”

The researchers recommend that shelters make more use of the “mixed breed” category when labeling new dogs.

They also recommend that public safety should shift its focus from persecuting specific breeds (and their lookalikes) to teaching people how to avoid dog bites.

Kate Horowitz is a science writer for mental_floss. She writes about pretty much everything, but especially likes to bring readers’ attention to squishy, underrated organisms; chronic illness and disability; science art; bodily functions; animal cognition; parasites; and the Moon. She lives in Washington, D.C., where she takes lots of walks and ogles other people’s dogs.